Galactoglycerolipid metabolism under stress: a time for remodeling.

Galactoglycerolipids are the predominant lipid building blocks of chloroplast membranes and are essential for plant growth. Plant chloroplasts harbor a constitutive set of UDP-Gal-dependent lipid galactosyltransferases that are responsible for the bulk of galactoglycerolipid biosynthesis. A set of paralogs is induced in response to phosphate deprivation, which leads to the remodeling of extraplastidic membranes with a partial replacement of phosphoglycerolipid by digalactosyldiacylglycerol. A third type of galactoglycerolipid biosynthetic enzyme, a UDP-Gal-independent galactoglycerolipid galactosyltransferase, was recently shown to be involved in freezing tolerance. Here, we look at how understanding of the regulation of galactoglycerolipid biosynthesis in chloroplasts by these multiple enzyme sets is rapidly evolving and discuss the increasingly recognized role of lipid remodeling in response to diverse abiotic stresses.